# std::match_results<BidirIt,Alloc>::str

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< cpp‎ | regex‎ | match results

string_type str( size_type n = 0 ) const; |  | (since C++11)

Returns a string representing the indicated sub-match.

If n == 0, a string representing entire matched expression is returned.

If 0 < n && n < size(), a string representing nth sub-match is returned.

if n >= size(), a string representing the unmatched match is returned.

The call is equivalent to string_type((*this)[n]);

`ready()` must be true. Otherwise, the behavior is undefined.

### Parameters

n | - | integral number specifying which match to return

### Return value

Returns a string representing the specified match or sub match.

### Example

Run this code

    #include <iostream>
    #include <regex>
    #include <string>

    int main()
    {
        std::string target("baaaby");
        std::smatch sm;

        std::regex re1("a(a)*b");
        std::regex_search(target, sm, re1);
        std::cout << "entire match: " << sm.str(0) << '\n'
                  << "submatch #1: " << sm.str(1) << '\n';

        std::regex re2("a(a*)b");
        std::regex_search(target, sm, re2);
        std::cout << "entire match: " << sm.str(0) << '\n'
                  << "submatch #1: " << sm.str(1) << '\n';
    }

Output:

    entire match: aaab
    submatch #1: a
    entire match: aaab
    submatch #1: aa

### See also

operator[] | returns specified sub-match (public member function)

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